hmmm... Ask your "famous tuner" check out the before/after dyno posted at the beginning of this thread-- it was done with the factory CAT. "No point" indeed . That torque curve is pretty impressive for an OEM CAT and a sub $200 generic header for the masses. I would certainly agree there is potential for MORE torque/HP in the upper RPM band with an aftermarket CAT.

 

Yes, I can see the dyno result and it is impressive ! That's the reason why I am confused.

 

I PM'd JLM asking about his recommendations for OBD 2 aftermarket cat. He did not respond. I also would like to know what is recommended, esp. a cat with an after cat bung already welded in. I am not up for cutting up the $1000 factory header in case I need it to pass smog inspection. The rules seem to indicate you can't just replace cats without the technician saying it was necessary, due to fed smog rules.

 

why would anyone look? This might be found at a secondary inspection if you'd been labeled a gross poluter, but I don't see anyone looking under my car when I get smogged. So there is technically a reason to worry, but not really a practical one. Also, if you bought your car in CA, you won't get smogged for the first five years you own the car. That gives some time for dirt and the like to build up, and who will be able to say what part is there

As far as the cats go, aftermarket cats do the same thing as OEM cats do. So you shouldn't worry there either. Someone used a cat from a cheby 350 (that should have enough flow), but I'm not sure if it was smog legal either.... Anyway, if CARB complience is manditory for your parts, you will have a much more limited selections than guys like me who don't care about the label, but sill want clean exhaust...... Also, I don't think there's such a thing as OBD II cat, but there are cats that have CARB approval and those that don't. OBD II has to do with sensors and interface and systems checks.


Matt

 

Guys, should I get a new 200cell CAT or stick with the OEM CAT. Any difference?

 

http://www.hottexhaust.com/search_re...&btnSearch.y=8

http://www.performancedepot.com/pdal...d22c2e554b7b70

etc

 

I would, purchase one of these two CAT's,
91000
SINGLE SENSOR OBD2 compliant for CARB 4L or EAP 4.2L engine @ 4500lbs.
provides a single O2 sensor boss
IN/OUT 2.50" MAGNAFLOW part # 91036
SIZE 13" over all L, body L 9", 6.5" over all W, 4" thick.
Retail Price: $72.59
[size=2]Your Price: </I>$65.99[/size] < great price PERFORMANCEDEPOT.COM
If I also wanted to equip. it with a Wide Band o2 sensor for fuel logging in addition to the OEM o2 sensor,
The 43000 series converter with two O2 sensor bosses.
IN/OUT 2.5" MAGNAFLOW part # 43066
didn't look up best price, but figure around $110.00 tops.

Dr Obnxs, I used a CAT for a GM 350 (that should have enough flow) (it did!), but I'm not sure if it was smog legal either.What me worry, it passed with flying colors! In MD the first thing they do at emissions is look at the dash for a check engine light on, that will fail you right there, then they plug into your OBD2 port and look to see if the OBD2 is in read ready state if not, you fail. If you have made it this far they put your car on a rolling dyno with a sniffer up the tail pipe and run the car up to a couple steady speeds and take pass/fail readings. This happens every two years, Cal. doesn't have a choke hold on the smog stuff for sure.
They have mirrors on little wheels to look under your car for a CAT but I really don't think anyone there knows the differences, if it looks like a CAT then its a CAT, ya Know.
Veni_Vidi_Vici, Thanks for the links.

This ain't rocket science folks, it's hard parts, pipes and stuff.

 

norm03s,

I take it you haven't had any problems with P0420 Catalyst System Efficiency Below Threshold? This problem shows up a lot in the VW 1.8T and different cat companies have different success rates with it:

http://forums.vwvortex.com/zerothread?id=663057

 

have a down stream 02 sensor code after about a year. I checked the CAT internals and it looked like it was lighting off. The sensor was carboned up though, so I cleaned it,the throttle body, K&N, new plugs, put the OEM wires back on ( removed the Nologys) new OEM PVC valve. I ran a strong load of injection cleaner through it other than my normal Redline injection cleaner and reset the ECU by disconnecting - Bat cable. Not all in that order. CEL was out, life was good then it came back on. So I went down a bought a new down stream 02 sensor reset the ECU, no problems since.
I left this out, I read the VW forum link to, thanks.
When I adapted that CAT to mate with the header collector I added the down stream 02 bung about 6 in. before the CAT as the OEM down pipe had the 02 before the CAT.

 

I thought I'd post a 4 week update on my OBX/OEM CAT install. During this time, I did a 1200 mile trip to north Italy, and my 44 mile round trip commute to work. I drive somewhat spirited for most passenger's taste. The car has developed or I've noticed a very low tone drone at 2800-3100 rpm. I simply cruise above or below this to avoid it. Its a small window. This past weekend I slipped in a set of these from Mini Mania:

They took the drone out, and nothing else. No performance hit noticed. Perfect.

Put Blu on a lift yesterday and spent a couple hours under, checking the OBX, the header-to-CAT butt-weld, and the OEM CAT. I also did a little adjusting on the joints of my Boral Exhaust to make sure I wasn't getting any mis-alignment stress on the system. I was getting a small rattle from the exhaust tips bumping into the rear facia at idle - cured.

Naturally, the header is developing some bluing. Head to header bolts still nice and tight. Found no visual evidence of weak header welds - all appear good. The CAT/Header butt-weld looks great with no visual evidence of fatigue. The CAT looks the same as it always has, inside and out.
I'm still thrilled with the install.

 

My header went on today, about time. Sparktec came thru with the missing gasket and the rest is history. I like it, it makes the milltek catback bark. It also made the brute get a little stroger, I can feel the difference from the stock header. I drove from helix back to N.Y. a happy guy, I also got the helix ssk, awsome. I was shifting from 6th to 4th and 6th to 3rd and it was perfect. The header is good bang for the money so far, we'll see about it's durability. They are so cheap I purchased a second one just in case I have a problem with the first. Thanx to all who contributed in my research and saga, very much apreciated.

 

Been driving around with the obx header, it is surprisingly quiet even at 3000 rpm's highway cruising. Excellent bark at wot, rocks the milltek catback. Stoked on the sound and extra torque.

 

I am thinking of going the same route and get myself a header in the coming weeks. Did you have to re-tune the GIAC after the header install?

 

No I did not need a new giac flash to go with the obx header. I have a spare obx header, I purchased 2 because they are so afordable. I don't think I'm going to need it, if you want it I'll sell it to you for my cost.

 

I installed the OBX in my MINI S this past weekend. Before I bolted it to the engine, I lined up the stock and OBX header to insure that the bolt holes lined up properly. Yes they do, perfectly. I noticed that the stock gasket had a lot of exhaust build up around the openings of the gasket. When I lined up the stock gasket to the gasket OBX provided, big difference. Somebody suggested the use of the stock gasket with the OBX header. I would suggest that you use the gasket OBX provides.

Now for the new information in this subject. I had to drive the car with the OBX header installed and the stock exhaust (past the Cat). This created a gap about 12 inches long between them. That is wide open exhaust from the engine to the tip of the OBX header. The first oxygen sensor was in place in the OBX header. The second one was tie wrapped to the stock Catback exhaust. Get this, NO ENGINE WARNING light came on while driving the 12 miles to the muffler place.

I used earplug in the car and tried to keep it below 2k RPMs. Otherwise it was so loud that I could not stand it. The whole car was shaking with the noise. Way too loud ......

After the installation of the stock CAT was complete, it was not much louder than stock. This was important to me. I want a sleeper.

Low end torque is up, without a question. Mid range feels also stronger, but not as obvious as the low end. Not tried the high end yet. I am all smiles with this mod. I am considering doing the one ball mod. The price is apealing. If anyone has this combination, OBX header with the stock cat and the one ball mod, please let me know your experience and opinion. Thanks.

Bomboasy

PS. The OBX header cost me $187 including shipping. $50 for modifying the CAT to fit the OBX header. The seller at Ebay put me on contact with his source and they told me that they just got in the CatBack from OBX for the MINI S. I am waiting for a picture and price.

 

Posting some pictures in case anyone is interested. They show the difference between Stock vs. OBX Gasket, oxygen sensor location and overall construction. So far, it has made so little impact on the noise level that I am probably going to go with the One Ball mod.

bomboasy

 

What is the one ball mod? bomboasy, did you eliminate the pre-cat? What did you do with the second sensor? Do you have any photos under the car of the modified area? I have my header, just trying to get it all straight before trying to install.

 

The one ball mod removes the resonator and diverts the exhaust directly to the stock muffler in the driver side. Look at this thread for more details.

https://www.northamericanmotoring.co...ad.php?t=39301


I installed the OBX header after removing the stock header. The shop cut the stock header at the CAT. The Cat, opening for the second oxygen sensor and flange that attaches it to the catback would be the piece that you keep. Weld that to the little piece, looks like the end of a trumpet, that comes with the OBX.

"what comes in the box?
I just got my obx header and think I'm missing something, here is what came in the box:
1. Head/header gasket
2. header
3. small joint pipe and flange
4. 2 bolts, nuts and springs

I think I'm missing some kind of gasket for the flex joint
I'm missing the round gasket for the flex joint." From MINIBRUTE



Make sure that you look for the gasket that seals the flex joint, from OBX and if you do not have it, get it before you actually make the installation.

I will take pictures today to show you the end result.

Bomboasy.

 

Here are the photos that I promised....:smile: I also modified one of the photos in my previous post, make sure to take a look again.

Bomboasy

 

Great photos. Exactly what I was hoping to see. Thank you very much.

 

Is there any header/cat solution that is 100% bolt on? I would rather do all the work in my garage, rather than go to a muffler shop. I do not have the skills nor equipment to weld, but I can turn a wrench. Thanks!

matt ma

 

Not at this price range. This is a racing, not street, header that we are modifing to the street. You can find plenty of other bolt on complete exhaust systems available at many times the price of this product. For the header, it is the CAT that adds cost. Buy one with a CAT and you pay for it.

Bomboasy

PS. Still very happy with this mod.

 

The install is really not a big deal. Yesterday I removed the old header, and installed the new OBX in about 2 hours in the driveway. Then drove (slowly) to a nearby muffler shop with the open header, and had the shop cut off the old CAT and weld it in just as shown in Bomboasy's photos from this thread. Welding cost $50, and everything is done. Really very easy install, and no welding needed by you, let a shop do the welding.
One thing suprised me, that was how badly the car runs (?) on an open header! REALLY rough, horrible response etc. It points out how important a well engineered, tuned exhaust system is to the performance of the car.

My thoughts: this is a very nice header for an amazing price. So much better made than the original. Perfect fit with quality welds and finish. When combined with my magnaflow exhaust, the sound is not louder, in fact it may have reduced some resonance, and made the tone a bit more defined. Need to put on more miles before I can really evaluate any performance change.

 

So everyone is getting the OBX part number 10350? One seller on ebay has the same part number for the non S. Must be the same header for both.

Brad

 

DK23,
I used earplugs. To me, it seemed like the car would fall apart if I got anywhere past 4K rpm. The noise and vibration was unreal. I spend a LOT of time in airboats and never seen those wide open engines, think 454 at 6k rpm and no CAT or Muffler, vibrate like that. Man it was loud.

nerd, I like saying that, I do not know the part number. I will see if I can find it in the staff that was in the box, if I still have it.

Bomboasy